Advances in technologies associated with electrical circuitry have led to great improvements in many fields. For example, the miniaturization of transistors has enabled computational speeds and data storage capacities for computers that were considered impossible only a few years ago.
The field of nanotechnology, involving materials formed and utilized on a nanometer scale, has developed over the last several years as the next step in the ongoing attempt to further miniaturize materials. Some of the most exciting materials to be discovered in the field of nanotechnology are carbon-based nanostructures including single-walled nanotubes (SWNT), multi-walled nanotubes (MWNT), and solid carbon nanowires. Carbon-based nanostructures exhibit many desirable properties including high tensile and mechanical strength, good flexibility, large surface area, light weight per unit length, high thermal conductivity, the capacity to conduct very high current densities, e.g., exceeding 107 A/cm2, and, in the particular case of SWNT, the capacity to be either metallic or semiconducting, depending on chirality of the structure.
The properties of carbon nanostructures make them excellent candidates for incorporation into many devices. Unfortunately, high yield methods for forming quantities of carbon nanostructures having particular electrical or structural characteristics have proven difficult and expensive to develop. For example, methods that have been developed to form isolated SWNT (as opposed to, for instance, a mat, a felt, or a rope of SWNT) have often involved the formation and utilization of a particularly patterned substrate (see, for example, ‘Synthesis of individual single-walled carbon nanotubes on patterned silicon wafers’. Kong, et al., Nature, 395, pp. 878-881 (Oct. 29, 1998)). Similarly, methods for forming nanostructures having a particular shape, for instance nanostructures that are coiled along their axial length, are generally quite complicated, with little control as to particular product characteristics. For instance, Nakayama, et al. (U.S. Pat. No. 6,558,645), disclose a formation method for producing nanocoils. The reference teaches a fairly high yield of nanocoils (e.g., 95%), but the process calls for pre-formation of complicated nucleating particles, which increases costs. In addition, many known processes that can form particularly shaped nanotubes or nanowires form the desired product materials mixed with MWNTs of other shapes, adding an additional separation step to the process in order to obtain any amount of the desired product in a purified state.
Moreover, as the ability to produce large quantities of nanostructures having particular characteristics has proven so difficult, the incorporation of such structures into useful end products has been slow to develop as well. In fact, due to the difficulties associated with forming particularly tailored nanostructures in bulk, many such materials have yet to be examined in detail, and characteristics of the materials, for instance the electrical characteristics of many structures, have yet to be fully understood. The ability to form in bulk nanostructures that have been tailored to a specific design could lead to a better understanding of the characteristics of the materials, which could in turn open the door to uses for these materials that have not previously been considered to be possible.
What is needed in the art is a relatively simple method for producing carbon-based nanostructures that can offer a high degree of control to the production process, in order to provide high yields of essentially identical nanostructures. In addition, what is need in the art is a method that can be easily adapted, providing a relatively simple route for tailoring the characteristics of the product nanostructures to meet pre-determined specifications.